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Q1 (A): What does the MRI in figures 1 and 2 show?
The MRI scans of brain (fig 1 and 2) show high signal lesions of the same age on T2 weighted images in various parts of the subcortical white matter, midbrain, and cerebellum. Large confluent lesions are seen in the right subcortical region. These features are seen in acute disseminated encephalomyelitis (ADEM).
Q1 (B): What further tests would you perform on the CSF?
The additional test done on the CSF of this child was oligoclonal banding, which was positive. Oligoclonal bands of IgG, although more commonly seen in multiple sclerosis, can also be seen in ADEM as in the present case. Persistence of oligoclonal bands in serial CSF examinations suggests multiple sclerosis.1
Q2: What is the treatment and prognosis for this condition?
The treatment of choice is high dose methyl prednisolone followed by a tapering dose of prednisolone over several weeks. This considerably decreases the rapid progression of symptoms and allows for a quicker and more complete recovery.2 In severe cases, plasma exchange has been tried and there are a few reported cases in literature that seem to have responded to intravenous immunoglobulin. The prognosis for recovery is very good, although relapses may occur in a third of these patients.3
Q3: What other conditions may have a similar clinical presentation and MRI picture?
Multiple sclerosis is one of the close differential diagnoses. Although no clinical feature can categorically distinguish the two, there are a few differences between the two conditions. ADEM usually presents with multifocal neurological signs and widespread central nervous system involvement, whereas multiple sclerosis usually presents as a monosymptomatic syndrome with optic neuritis, subacute myelopathy, or ataxia. Seizures, changed sensorium, and other signs of grey matter involvement are uncommon in multiple sclerosis. Simultaneous symmetric optic nerve involvement does point to ADEM whereas optic neuritis in multiple sclerosis is usually unilateral. MRI scan of the brain can help distinguish ADEM from multiple sclerosis. In ADEM, the white matter lesions are typically large, extensive, and often asymmetrical involving the adjacent grey matter. In multiple sclerosis the plaques are typically small, circumscribed, and symmetrical in the deep white matter. In ADEM the lesions are typically of the same age, while in multiple sclerosis they are usually of different ages. MRI changes usually tend to appear earlier in the course of illness in ADEM.1,4
ADEM is a monophasic multifocal inflammatory demyelinating disorder that is immune mediated.5 A temporal relation with immunisation to pertussis, diphtheria, measles and mumps has been noticed.6 It often follows viral infections during the recovery phase. Prodromal symptoms like headache, low grade fever, and myalgia often precede acute central nervous system symptoms. The central nervous system symptoms can take the form of motor deficits, cranial nerve palsies, brainstem, cerebellar, and sensory defects. Neurological symptoms are acute in onset and features of encephalopathy, meningismus, and seizures often confuse this with meningoencephalitis.7 Abnormal findings include areas of demyelination and areas of lymphocyte and macrophage infiltration. Several mechanisms have been proposed some of which include a complex interplay between cytokines, chemokines, and adhesion molecules. Tumour necrosis factor may also play a significant part.8 Although ADEM is usually considered to be a monophasic disease, relapsing and multiphasic cases have also been reported in the literature. Recovery can begin within days and complete recovery can take weeks to months. The diagnosis is based on clinical features described above with characteristic MRI lesions.1,4 The distinction between multiple sclerosis and ADEM is important because of prognostic and therapeutic implications, as ADEM is often monophasic and leads to a complete recovery whereas multiple sclerosis can lead to progressive deterioration over many years.9
Acute disseminating encephalomyelitis (ADEM) should be considered in the differential diagnosis of children presenting with changed sensorium and acute central nervous system deterioration.
ADEM is diagnosed on the basis of demyelination with multifocal central nervous system involvement seen clinically and on the MRI scans.
The computed tomogram of the brain may be normal and the MRI scan of the brain is diagnostic in most cases. MRI of the brain should be considered in the early stages of presentation because the prognosis depends on the early institution of effective treatment.